G424 Service Manual Gasoline Fuel System61
This system provides adequate air-fuel-mixture
richness for smooth engine running ranging from slow-
idle to light-load operation.
Fuel from the float chamber is sent through the main
jet to the pilot jet where metering of fuel is made.
On the other hand, air entering the venturi air leak and
that entering the pilot air jet No.2 join at the pilot air jet
No.1 where metering of air is made. As a result of
metering, fuel mixes with air and flows through the air-
fuel-mixture passage to the pilot outlet. The flow of air-
fuel-mixture is adjusted properly by the bypass screw
and enters the air horn through the bypass hole or the
pilot outlet. It mixes with the small amount of air that
gets past the closed or slightly opened throttle valve.
The final mixture flows into the engine cylinders.
The mixture adjusting screw is used for adjusting the
richness of air-fuel-mixture necessary for good idling.
The bypass screw is for the purpose of adjusting the
flow of primary air-fuel-mixture to the bypass hole so
as to provide sufficient mixture richness mainly for
engine operation ranging from “off idling” to a part of
medium-load operation.
The fuel cutoff solenoid in the idle system functions as
follows : When the key switch is turned to ON, the
solenoid attracts the needle valve to open the fuel feed
line. When the key switch is turned to OFF, the needle
valve protrudes to cut off the fuel feed line, thus
preventing spontaneous running of the engine which
is overheated.
3. Idle system
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